<!DOCTYPE>
<html>
<head>
<style>
    #background {
        width: 200px;
        height: 200px;
        background-color: red;
    }
    .blue {
        width: 50px;
        height: 50px;
        background-color: blue;
    }
</style>
</head>
<body>
<div id="background">text
    <div class="blue">
    </div>
</div>
</body>
</html>
